Frost dates for 78666San Marcos, TX
The average last spring frost in San Marcos is February 28 and the average first fall frost is November 29, giving a typical growing season of about 273 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- Feb 28
- Average first fall frost
- Nov 29
- Growing season
- 273 days
Safer after Mar 21 (1-in-10 risk)
Possible by Nov 8 (1-in-10 risk)
First frost typically in 33 days
Frost risk by date
NOAA reports frost dates as probabilities. The middle date is the average (a 50% chance). For spring, the 10% date is a safer planting date: frost after it happens in about 1 year in 10. Light frost (36°F) can damage tender plants; a hard freeze (28°F) kills most annuals.
| Temperature | Last spring: 90% / 50% / 10% chance | First fall: 10% / 50% / 90% chance | Growing season (50%) | Years with at least one |
|---|---|---|---|---|
| Light frost (36°F) | Feb 23 · Mar 14 · Apr 5 | Nov 1 · Nov 16 · Dec 4 | 246 days | 100% |
| Frost / freeze (32°F) | Feb 1 · Feb 28 · Mar 21 | Nov 8 · Nov 29 · Dec 21 | 273 days | 100% |
| Hard freeze (28°F) | Jan 9 · Feb 13 · Mar 8 | Nov 19 · Dec 15 · Jan 13 | 306 days | 98% |
Planting calendar for San Marcos
Planting windows from the University of Maryland Extension calendar, shifted to your average frost dates. Use them as a starting point and adjust for seed packet instructions and local conditions.
| Crop | Task | Window |
|---|---|---|
| Tomatoes | Start seeds indoors | Jan 28 – Apr 5 |
| Tomatoes | Transplant outdoors | Mar 16 – Aug 9 |
| Peppers | Start seeds indoors | Jan 28 – Feb 28 |
| Peppers | Transplant outdoors | Mar 30 – Apr 30 |
| Eggplant | Start seeds indoors | Feb 14 – Mar 15 |
| Eggplant | Transplant outdoors | Mar 30 – Apr 30 |
| Cucumbers | Sow outdoors | Mar 30 – Aug 19 |
| Summer squash | Sow outdoors | Mar 16 – Apr 30 |
| Winter squash & pumpkins | Sow outdoors | Mar 30 – Apr 30 |
| Snap beans | Sow outdoors | Mar 16 – Sep 11 |
| Sweet corn | Sow outdoors | Mar 16 – Aug 9 |
| Watermelon & cantaloupe | Sow outdoors | Mar 30 – Apr 30 |
| Okra | Sow outdoors | Mar 23 – Apr 15 |
| Peas | Sow outdoors (spring) | Jan 28 – Mar 15 |
| Potatoes | Plant outdoors (spring) | Jan 28 – Mar 30 |
| Onions | Start seeds indoors (spring) | Dec 17 – Jan 13 |
| Onions | Transplant outdoors (spring) | Feb 14 – Mar 15 |
| Broccoli | Start seeds indoors (spring) | Jan 10 – Feb 13 |
| Broccoli | Transplant outdoors (spring) | Feb 14 – Mar 15 |
| Broccoli | Start seeds indoors (fall) | Jul 30 – Aug 9 |
| Broccoli | Transplant outdoors (fall) | Aug 29 – Sep 9 |
| Cabbage | Start seeds indoors (spring) | Dec 31 – Jan 28 |
| Cabbage | Transplant outdoors (spring) | Jan 28 – Feb 28 |
| Cabbage | Start seeds indoors (fall) | Jul 20 – Aug 19 |
| Cabbage | Transplant outdoors (fall) | Aug 19 – Sep 19 |
| Leaf lettuce | Sow outdoors (spring) | Jan 28 – Apr 15 |
| Leaf lettuce | Sow outdoors (fall) | Aug 19 – Oct 5 |
| Spinach | Sow outdoors (spring) | Jan 21 – Mar 6 |
| Spinach | Sow outdoors (fall) | Sep 5 – Oct 10 |
| Radishes | Sow outdoors (spring) | Jan 28 – Mar 20 |
| Radishes | Sow outdoors (fall) | Aug 19 – Oct 20 |
| Kale | Sow outdoors (spring) | Feb 14 – Mar 6 |
| Kale | Sow outdoors (fall) | Aug 12 – Sep 19 |
| Carrots | Sow outdoors (spring) | Feb 28 – Apr 15 |
| Carrots | Sow outdoors (fall) | Jul 20 – Sep 4 |
| Garlic | Plant outdoors (fall) | Nov 19 – Dec 20 |
Where these dates come from
ZIP code 78666 is matched to the NOAA station San Marcos, TX, 1.2 km away, at 665 ft elevation (88 ft higher than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| San Marcos, TX (used) | 665 ft | Feb 28 | Nov 29 |
| New Braunfels Wfo, TX | 628 ft | Feb 25 | Nov 25 |
| Austin San Antonio, TX | 633 ft | Mar 1 | Nov 26 |
| Canyon Dam, TX | 1,000 ft | Mar 1 | Dec 1 |
Frost dates near San Marcos
- Martindale, TX 78655 · last Feb 28, first Nov 29
- Maxwell, TX 78656 · last Feb 28, first Nov 29
- Staples, TX 78670 · last Feb 28, first Nov 29
- Kyle, TX 78640 · last Feb 28, first Nov 29
- Fentress, TX 78622 · last Mar 5, first Nov 23
- San Marcos, TX 78667 · last Mar 17, first Nov 13
- New Braunfels, TX 78130 · last Mar 1, first Nov 26
- Wimberley, TX 78676 · last Mar 1, first Dec 1
Frequently asked questions
- When is the last frost in San Marcos, TX?
- For ZIP code 78666, the average last spring frost (32°F) is February 28, based on NOAA 1991-2020 climate normals for the San Marcos, TX weather station. There is a 1-in-10 chance of a frost after March 21.
- When is the first frost in San Marcos, TX?
- The average first fall frost (32°F) is November 29. There is a 1-in-10 chance of frost by November 8, so tender plants are at risk from that point on.
- How long is the growing season in 78666?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 273 days long.
- Are these frost dates a forecast?
- No. They are 30-year averages and probabilities from NOAA weather station records. Use them to plan, then watch your local forecast before planting tender crops or leaving them uncovered.